Process for the manufacture of dienes



May 29, 1945;- f,

B. H. SHOEMAKER PROCESS FOR THE MANUFACTURE 0F BIENES Filed June 25, 1942 Ber 1,2, www

Patented May 29, 1945 UNITED STATES PATENT ortieigfff aztecas', l y

Bernard H. Shoemaker, Hammond, Ind., assignor to Standard Oil Company,

lporation of Indiana Chicago, Ill., a cor- Appucatian June 25, 1942, serial No. 448,336

s claims. A (ci. 26o-680) This invention relates to the preparation of dienes from hydrocarbons and .from compounds of sulfur with hydrocarbons. More specifically, the invention relatesV to the preparation of dienes from alkyl sulfides and still more specifically, butadiene from dibutyl .disulfide by a pyrolytic reaction.

Numerous processes have been proposed for converting parailin and olen hydrocarbons into dioleflns, and particularly into butadiene and iso'- prene. The formation of butadiene from paraffins and olefins, however, is beset with the difficulty that whereas the parafilns and oleflns are very stable and relatively unreactive, the dienes are notable for their high reactivity and particularly their tendency to polymerize. Accordingly,

lthe processes heretofore proposed for the prepper, iron or iron sulfide catalysts. TheA generalv reaction is indicated as follows:

The next stepin the process involves the conver sion of the disulfide to the diene by heating with or Without the presence of 'a catalyst. A catalyst of the dehydration or dehydrosulfurization type peratures of the order of 400, to '700 C. may be is employed. Copper, zinc, cadmium or silver suliides are eiective and I may also use aluminum oxide, magnesium oxide, chromium oxide, tung-l sten oxide, cobalt or molybdenum sulfide, alone or in combination. Dehydrosulfurization tememployed. l

The dialkyl disulfide, for example, dibutyl disulde, prepared. as indicated is subjected to de- "sulfurization by contacting with the catalyst at a high'v'elocity, a space velocity of about 1 to 20 being commonly employed. The reaction is as follows:

.v Butylene and hydrogen sulfide which are pro- This application is accompanied by a drawing showing a rlow diagram of the process.

In accordance with my :procesal may prepare butyl mercaptan by various methods such as the treatment of butylene with hydrogen shown .by the following reaction:

Other methods may be used for preparing butyl mercaptan, for example the treatment of butyl alcohol with phosphorus sulde, the treatment of butyl chloride with esodium sulilde or the heating of butane with sulfur. Normal butyl mercaptans are desired and. particularly the secondary butyl mercaptan.

sulilde as duced in the reaction may be recycled to the system for further treatment.

`When a trisulfide is employed a larger yield of butadiene is anticipated as shown by the following reaction:

' Also, when dehydrogenating catalysts of high efflciency are employed. at high temperatures, it appears that one of the reactions occurring involves the formation of hydrogen, viz:4

g, i'lde produced as intermediates in thek process The second step of f the process involves the conversion of butyl mercaptan to a sulide, such as dibutyi disulfide, by an oxidation reaction.

This lis convenienuy accomplished by oxidizing with sodium hypochlorite in the presence of an alkali, for example, sodium hydroxide. Other.

oxidizing agents may be used.r Thus, sulfur may be used in the presence of sodium plumbite, or

air may be employed' in' the presence of copper chloride or other coppersalt solutions at ordi-J nary temperatures or at elevated temperature. in the presence of contact catalysts such as copmay be isolated' or they may be employed as they occur in the products of the reaction wherein they are produced. Thus, in the oxidation of butyl mercaptan with air, the reaction product vapors containingV butyl disulde may be conducted directly through the contactdehydrosulfurization catalyst toy convert the disulde into butadiene which may then be recovered from extraneous gases by condensation or by absorption in an absorption liquid, charcoal orother suitable adsorbent for thediene. In general,` however, I prefer to separateand-purify the alkyl sulfide intermedlate product before nal conversion,

The following example shows the formation of -atl elevated temperature.

buts sie fiom normal butyl disumae. 'me a1- sulflde'fwas contacted witna copper suliide catalyst at a temperature of about 543 C. "I'heerate of contact, or space velocity, was 1 volume of liquid'disuliide per hour per gross volume of cata- -lyst. The product freed from HzS gave the fol- A small amount of nitrogen was employed with' the disulde in this run. Hydrogen sulfide resulting from the reaction may be recovered.

When isoamyl disulde is employed in this reaction. the product formed on dehydrosulfurization is isoprene. Other alkyl sulfldes give other dienes.-

In another modicationv of. .my process, I may prepare mercaptans from hydrocarbons, for example; the C4 fraction obtained from petroleum distillationand cracking, by treating with hydrogen sulfide at elevated temperatures, preferably by passing a mixture of hydrocarbonsand Has into contact with a suitable catalyst maintained Mercaptans mayv be separated from the products of this reaction .and

processed as hereinbefore described or the entire i reaction product maybe converted with an oxidizing agent directly tothe disulde which may be recovered and subsequently converted into the 'I'he temperatures employed in the dehydrosulfurization step are usually in the range of about 350 to 700 C. Low pressures .are ordinarily desirabler the pressure being generally atmospheric orsubatmospheric, although pressures of the order of to-50 pounds per square inch may be employed. Short catalyst contact time in the range of 0.1 to 6. seconds is desirable, and contact times in the range of .01 to seconds may sometimes be used. v

It is desirable to cool the products of reaction rapidly after withdrawing them from the dehy-A drosulfurization step. Rapid cooling'may be obtained by introducing a quenching fluid directly into the reaction products, a suitable fluid being cold inert-gases recycled in the system, water, oil,

etc. Thus the products, hot from the reaction,

may pass directly into a cold water spray. The

water or other quench liquid may be recycled.

When applying myY process to the C4 fraction y Iof hydrocarbons recovered from petroleum processing,--for example, from. the cracking or reforming of hydrocarbons containing about 12 to :20% of isobutylene and about 20% of normal butylene, a mixed isobutyl-normal butyl disulfide maybe obtained which on dehydrosulfurization yields butadiene and isobutylene as indicated by` the followingequation:

'Ih'e isobutylene may be recoveredfrom the prod-v uct andv employed in otherrprocesses, for example, it may be Mmmm@ meenam the Prevlowing analysis: Y j

u Per cent Olefins '14.5 Butadienel 10.1 Parailins 11.8

Air a CO2 0.6

asvebas eration of antiknock motor fuels or it may be polymerized to synthetic lubricating oils, resins, synthetic rubber, etc. Isobutylene may also-be added, preferably in amounts not' exceeding equal molecular amounts to normalbutylene, and the mixed hydrocarbons may be treated by my process as hereinabove described, the isobutylene being recycled. In general, however. I prefer to isolate the normal butylenes from the C4 mixture before converting to the suldes. Also,l I prefer to use the -disecondary butyl disulfide.

- In another modication of my process the yiel of butadiene obtained from the dehydrosulfurization of dibutyl disulilde may be increased by introducing sulfur vapor or oxygen into the dehydrosulfurlzation catalyst' simultaneously with l suldes and polysulfldes, and mi tures of dienes may be obtained which may be either separated or used in the form of mixtures, if desired, in the nal conversion step. Unreacted olei'lns or parailns may be separated from the desired dienes by azeotropic or extractive distillation in' the presence of polar solvents in the manner known to the art. y

My process may be better understood by refer-l ring to the drawing which `yhows diagrammatia cally -on'e procedure for carrying it out. Referring to the drawing, butyl'ene, preferably one of the normal butylenes, butylene-l or butylene-2, or a mixture of them either alone or with other hydrocarbons or inert gases, is introduced by line 10 to catalytic reactor 11 along with hydrogen sulfide added by line 12. On contact with the catalyst, for example, zinc sulfide, aluminum oxide, etc., at a moderately high temperature in the range of 200 to 500 C.,- there is formed butyl mercap-l tan, the secondary butyl mercaptan generally predominating over the primary compound.

The reaction products from il are passed -by line I3 to fractionator I4 where the mercaptan is condensed and withdrawn at the. bottom. The unreacted gases, butylene and H28, are recycled to the reactor Il by line i5. The mercaptan is conducted by line I6 to reactor i1 where it is converted to the disulfide by reaction with air admitted by une ls. A suitable catalyst for re;

actor Il is iron, copper, iron sulfide, etc., the reaction temp'erature being moderately low, of the order of to 200 C. The product from l1 is passed by line I9 to fractionator 20 where the butyl disulfide is sep-v arated from the lighterv products and unreacted gases which may be discharged by vapor line 2l.vv

The butyl sulde is withdrawn from 20 by Aline 22 and charged to reactor 23 where it is contacted with copper suliide or othersuitable contact catalyst hereinbefore described-employingl a relatively high temperature and'short contact time. In reactor 23 a substantial proportion of the butyl sulfide is decomposed to butadiene and hydrogemsulflde, a substantial `amount ofy by product butylene being-obtained in-some cases.

A controlled amountof air or sulfur vapormay ,cycled through pump 2l land line Il.' Fresh make-up water may be added as needed by line 3l. Butyl vsulilde is withdrawn at a higher level by line ll and charged to iractionator 32 wherein it is separated from light products and residue, a

As indicated hereinabove. solvents suitable for about 350 to 700 C. and a contact time-within the range of about .01 to 20As'econds'," cooling the reaction products at a suiliciently rapid rate to avoid destruction of dienes and separating the desired diene from the said reaction products.

2. The process of claim 1 wherein the said alkyl sumae is a Vbutyl disumde.

3; The process oiclaim 1 wherein said alkyl sulilde isa normal butyl disulilde.

,4. The process of claim 1 wherein the said alkyl suiiide is a secondary butyl disulfide. 5. The process ofpreparing dioleilns which .comprisestreating an alkyl monosulilde with an oxidizing agent selected i'rom the class consisting this purpose are polar compounds, generally oxygen, halogen or sulfur compounds such as sulfuric acid esters. suli'o'nic acids, alcohols, aldehydes, ketones, esters and chlorine compOlmds in general. Phenol, aniline, cresylic acid, dichlori diethylether, and nitromethan'e may be specin.-

cally mentioned. The operation of fractionator 3! is simplified by the use 'of a relatively nonvolatile solvent such as phenol. 1f desired, Hi8 may be separated and removed by a pre-fractionation. step (not shown) in advance of fractionator- I.

In .fractionator 39 butadiene and the solvent descends through the column and are withdrawn by line 4I. leading to iiash drum 42 where the 'pressure is released and butadiene productY is discharged from the process by line I3, while the solvent is withdrawn by line 4.4 and recycled back to l! by line 40. Uncondensed gases, butylene,

Has, etc., are withdrawn from the upper part oi' iractionator I! by line 45 and recycled through Y valve 4I to reactor Il. When HzS isl present in 3l, it will contaminate. the 'product in line I3 to some extent and must be removed by in alkali otoxygen and sulfunin the presence of a dehydrosulfurization contact catalyst at a temperature within the range of about 350 to 700 C., cooling the reaction products at a sumeiently rapid rate to avoid destruction of dienes and separating th desired diene from said reaction products.

6. The process of making butadiene which comprises converting normal butylene into a butyl mercaptan by the action of hydrogenvsulfide in the presence of a sulfurizing catalyst, converting said butyl mercaptan to butyl sulfide by the action of an oxidizing agent, converting said butyl'sulflde to butadiene and hydrogen sulde by the action oi' a. dehydrosulfurizing catalyst at a temperature within the range of about 350 .to 700 C., and areaction time andyconcentration to produce a substantial yield of butadiene, recovering said butadiene and recycling said" hydrogen sulilde to the iirst step of the process.

7. The process vof making butadiene which comprises converting normal butylene into a butyl mercaptan by the action of-hydrogen sulilde in the presence ,of a suliurizing-catalyst. convertingsaid butyl mercaptan into butyl disulilde .by the action of an oxidizing agent, converting said butyl sulfide to butadiene and hydrogen sulfide by the action of a vdeliydrosulfurizingcatalyst at an elevated temperature within the dehydrosulfurization range and a reaction time and concentration to produce a substantial eld otbutadiene, recovering said butadiene the reaction products, separating hydrogen sulilde and f butylene from the reaction products and recysuldes, disulildesand polysulfldes. l

I claim:

1. The process of preparing dienes which comprises subjecting an alkyl sulnde havin! at least four carbon atoms to the action of a dehydrosui-g iurizing contact catalystat a temperautre ofi` cling said hydrogen sulfide and butylene to th lflrst step of the process.

-"8. The process of preparing diolens from unsaturated hydrocarbon gas mixtures containing olefins of at least i carbon atoms which comprises converting said oleflns to the corresponding alkyl sulildes, subjecting'said -alkyl sulfldes to the action of a dehydrosulfurization catalyst in the presenceoi controlled amounts of an oxidizing agent selected from the class consisting of sulfur and oxygen at a temperature within the range of about 350 to '700 C. and at a concentration `and reaction time at which said alkyl suldes are decomposed into hydrogen sulnde and dioleiins, and recovering said dioletlns from the reaction products.

, BERNARD H. SHOEMAKER. 

